My Little Pony XXXIV: There is Pony of it, no exceptions!

[vegetalss4]

To be fair, it depends on the situation. A earth pony that could write legably with is mouth could make a fortune on the novalty alown. A unicorn using magic would be nothing special, but juging from the one peice of actual writing we have, it would take a lot of time to learn eastern european-type letters. Hence the use of pictures on common items. Notably, most writing might be done by nonpony scribes, for thumbs would make things a whole lot easier to deal with the issuse of handling a pen. Not so much baby dragons, but creatures with actual hands like Dimond dogs or even griffons. As such, most things handwritten could be unicorn made, but others find it cheaper to have another creature to write it down.

I would note that we have seen more ponies write with their mouths, than we have seen Unicorns write with magic. So really I would think that earth ponies being able to write is more like basic education than any sort of novelty, remember the ponies do seem to have a rather fine manipulation through their mouths, not just in writing but also for hammering and painting and stuff.

This comment actually raised an interesting question for me. Is it possible to have bad writers in the pony universe? I'm sure there are some amateur writers around (e.g. Twilight's letters when her cutie mark is magic), but presumably anypony that pursued a writing career would get a writing cutie mark that would demonstrate her skill at writing. If a pony got some other cutie mark, she would be highly unlikely to go into a career as a professional writer.

Thinking about it, the only way I could see the pony universe relying on bad writing for major productions would be if writing cutie marks were so rare that there aren't enough of them to go around. And if that were true, pony writers might be in high demand and would live very wealthy and comfortable lives when they weren't writing.

...And somehow I just reached the conclusion that good fanfiction writers could get ponified and live like kings/queens.

I would imagine that not every writer has a writing cutie mark, just the best of them. If nothing else there would be autobiographies written by famous ponies and text books written by ponies with marks about research of the subject at hand.
Now that I think about it, not even every celebrated writer would necessarily have a writing mark, I mean if Tolkien had been a pony he would probably have a linguistic cutie mark.